In 1994 and 1995, seven cases of Human monocytic ehrlichiosis were reported in Indiana; six cf these were from southern counties. To test whether Ehrlichia cha ffeensis is present in native ticks, adult ticks representing two species, Dermacentor variabilis and Amblyomma americanum were collected in southern Indiana during the first week of May, 1995 and tested by PCR. A total of 510 D. variabilis ticks were collected and placed into 102 pools (5 ticks per pool). A total of 430 adult A. americanum ticks were collected and placed into 88 pools of 5 ticks or less.D. variabilis ticks were used to optimize the isolation of PCR amplifiable DNA and determine the minimum number of bacterial cells detected. A modified CTAB-phenol method permitted the detection of as few as 100 bacterial cells. The optimal amount of isolated DNA for a PCR amplification was determined to be 2.7 pg of total nucleic acid.The 88 pools of adult A. americanum were subjected to DNA isolation, PCR amplification, and Southern analysis to determine the presence of E. chaffeensis bacteria. Using the 16S rRNA gene from E. chaffeensis, with species specific primers Hut and HE3. Of the 88 pools (430 ticks; 21 were determined to be positive for the presence E. chaffeensis bacteria. Thus, minimal field infection rate for adult A. americanum ticks in Southern Indiana was 4.88%. This calculation is based upon the assumption that at least one tick was positive in each positive pool. / Department of Biology

Human monocytic ehrlichiosis (HME) is a tick-borne infectious disease caused by the bacterium Ehrlichia chaffeensis and transmitted by the ixodid tick Amblyomma americanum. The first confirmed case of HME in Indiana occurred in 1994. Since then, there have been an additional 17 confirmed cases reported from 11 counties.A total of 498 A. americanum and 25 Dermacentor variabilis ticks were collected from counties in southern Indiana during May and June 1998, pooled, and examined for the presence of E. chaffeensis using nested PCR with primers HE 1 and HE3, which are specific for the 16S rRNA gene of E. chaffeensis. Ten pools of adult A. americanum specimens tested positive for E. chaffeensis DNA. This represented a minimum infection rate (MIR) of 3.82%. None of the A. americanum nymphs or adult D. variabilis ticks tested positive.In addition, 325 white-tailed deer blood samples from Indiana and 327 from Ohio were collected during November, 1998 and tested for the presence of E. chaffeensisreactive antibodies using an indirect immunofluoescence assay (IFA). Evidence of such antibodies was found in deer killed in six Indiana counties where infection rates ranged from 43% - 64% and four Ohio counties where infection rates ranged from 4% - 25%.The results from this study support the view that the distribution of E. chaffeensis closely follows that of A. americanum in the North Central United States. This is the first report of E. chaffeensis-reactive antibodies in white-tailed deer from Ohio. / Department of Biology